CHAPTER 8: SENSATION AND PERCEPTION. SECTION 1: SENSATION

CHAPTER 8: SENSATION AND PERCEPTION

SECTION 1: SENSATION

WHAT IS SENSATION?

• Def: what occurs when a stimulus activates a receptor

• Stimulus: an aspect of or change in the environment to which an organism responds

SENSATION CONTINUED• Perception:

organization of sensory info into meaningful experiences

• Psychophysics: study of the relationships between sensory experiences and the physical stimuli that cause them

THRESHOLD

• Absolute threshold: the weakest amount of a stimulus that a person can detect half the time

• Humans have a very limited range

SENSORY DIFFERENCES

• Difference threshold: the smallest change in a physical stimulus that can be detected between 2 stimuli

• Just Noticeable Difference (JND): the smallest increase or decrease in the intensity of a stimulus that person can detect

WEBER’S LAW

• For any change in a stimulus to be detected, a constant proportion of that stimulus must be added or subtracted

• A.K.A.: Weber-Fechner Law

SENSORY ADAPTATION• Senses are tuned to

change• Senses adapt to a

constant level of stimulation

• Necessary to ignore mundane

SIGNAL-DETECTION THEORY• Def: the study of

people’s tendencies to make correct judgments in detecting the presence of stimuli

• Radar operator

PROCESSING STIMULI

• Preattentive process: extracting information automatically

• Attentive process: procedure that considers only one part of the stimuli presented at a time

• Stroop Interference Effect

SECTION 2: THE SENSES

VISION

• Most studied sense• Pupil: opening in the iris

that regulates the amount of light entering the eye

• Lens: flexible structure that focuses light on the…

• Retina: innermost coating of the back of the eye, containing light sensitive receptor cells

VISION CONTINUED

• Cones and Rods: light receptors in the retina; convert light energy into neuronal impulses

• Cones: color• Rods: night vision• Optic Nerve: the nerve

that carries impulses from the retina to the brain

COLOR DEFICIENCY

• Affects 8% of American men; <1% women

• Dysfunctional cones• Red-green• Yellow-blue• Total deficiency: see in

black and white

BINOCULAR FUSION

• Def: the process of combining the images received from the two eyes into a single, fused image

• Retinal Disparity: the differences between the images stimulating each eye

• Essential for depth perception

NEARSIGHTEDNESS

• Eyeball is longer than normal

• Objects focused at a point in front of the retina

• See objects that are near, but not far

FARSIGHTEDNESS

• Eyeball is too short• Objects focused slightly

behind the retina• Distant objects are

clear, near objects are not

HEARING

• Sound waves: vibrations in the air

• Loudness determined by amplitude (height) of waves

• Strength determined by decibels

• >110 decibels damages hearing

HEARING

• Pitch depends on sound wave frequency (rate of vibration of medium through which wave travels)

PATH OF SOUND

• Outer ear (pinna) receives waves

• Auditory canal vibrates which vibrates the ear drum

• Middle ear: 3 tiny bones---hammer, anvil, and stirrup

• Inner ear: cochlea---liquid moves, tiny hairs detect motion, translate into neuronal input and sent to brain by the Auditory nerve

DEAFNESS

• 2 types:• 1) Conduction deafness:

hindered physical motion in the outer or middle ear

• Helped with conventional hearing aid

• 2) Sensorineural deafness: damage to the cochlea

• Helped with cochlear implant

BALANCE

• Vestibular system: 3 semicircular canals that provide the sense of balance, located in the inner ear and connected to the brain by a nerve

• Fluid in canals moves• Hair cells translate

motion

SMELL

• Chemical sense• Gaseous molecules

contact smell receptors• Olfactory nerve: carries

smell impulses from the nose to the brain

TASTE

• 5 primary tastes:• 1) Sweet• 2) Sour• 3) Bitter• 4) Salty• 5) Umami (savory, meaty)• Combination of these

creates flavor• Taste is more determined

by smell

SKIN SENSES

• Densely bundled nerve endings create sensitivity to pressure

• Some are sensitive to hot and cold

• Pain results from many different stimuli

PERCEPTIONS OF PAIN• Sharp, localized pain

immediately after injury• Dull, generalized pain

later• Gate control theory of

pain: shifting attention away from pain can lessen its effects

BODY SENSES

• Kinesthesis: the sense of movement and body position

• Cooperates with vestibular system and vision

• Receptors in and near muscles, tendons, and joints

SECTION 3: PERCEPTION

The way we interpret sensations and organize them into meaningful experiences

GESTALT

• Def: the experience that comes from organizing bits and pieces of info into meaningful wholes

• Trying to identify principles the brain uses in building perception

GESTALT PRINCIPLES

• 1) Proximity• 2) Continuity• 3) Similarity• 4) Simplicity• 5) Closure• If elements are close to

one another or similar, we perceive them as one set

FIGURE-GROUND PERCEPTION• The ability to

discriminate btwn a figure and its background

• Shows we can perceive in more than one way

• Works with sound as well

PERCEPTUAL INFERENCE• Filling in the gaps in

what our senses tell us• Largely automatic and

unconscious• Depends on experience

LEARNING TO PERCEIVE• Influenced by needs,

beliefs, and expectations

• If we want something, we’re more likely to see it

• Perceptual set: twisting truth to fit our own belief system

SUBLIMINAL PERCEPTION• Subliminal messages:

brief auditory or visual messages that presented below the absolute threshold

• Not really effective

DEPTH PERCEPTION

MONOCULAR DEPTH CUES• Can be used with a

single eye• Relative height: objects

further away are higher on your visual plane

• Interposition: overlapping

• Light and shadows: brightly lit objects are closer

MORE MONOCULAR CUES• Texture-density

gradient: close objects have more detail

• Motion parallax: the apparent movement of stationary objects relative to one another that occurs when the observer changes position

MORE MONOCULAR CUES• Linear perspective:

parallel lines converge in the distance

• Relative motion: near objects appear to move in the opposite direction that you do; far objects seem to travel with you

BINOCULAR DEPTH CUES• Depend on movement

of both eyes• Convergence: eyes turn

inward when looking at nearby objects

• Retinal disparity• Large disparity means

close; small means far

CONSTANCY

• Def: the tendency to perceive certain objects in the same way regardless of changing angle, distance, or lighting

ILLUSIONS

• Def: perceptions that misrepresent physical stimuli

• Happens when perceptual cues are distorted so our brains cannot correctly interpret space, size, and depth cues

EXTRASENSORY PERCEPTION

• Def: (ESP) an ability to gain info by some means other than the ordinary senses

• 4 types:• 1) Clairvoyance: perceiving

w/o sensory input• 2) Telepathy: mind reading• 3) Psychokinesis: move

things with your mind• 4) Precognition: foretell

events

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